Display device

ABSTRACT

A display device includes a first transistor provided with an oxide semiconductor layer, a first gate electrode facing the oxide semiconductor layer and a first gate insulation layer between the oxide semiconductor layer and the first gate electrode, a first transparent conductive layer in contact with the oxide semiconductor layer in a first contact area not overlapping the first gate electrode in a plan view, and a second transparent conductive layer connected to the first transparent conductive layer in a second contact area overlapping the first gate electrode in a plan view and provided in a display area of the pixel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2021-056085 filed on Mar. 29,2021, the entire contents of which are incorporated herein by reference.

FIELD

One embodiment of the present invention relates to a display device. Inparticular, one embodiment of the present invention relates to a displaydevice using a transistor having an oxide semiconductor.

BACKGROUND

Recently, a transistor using an oxide semiconductor as a channel hasbeen developed in place of an amorphous silicon, a low-temperaturepolysilicon, and a single-crystal silicon (e.g., Japanese laid-openpatent publication No. 2014-146819 and Japanese laid-open patentpublication No. 2015-159315). The transistor using the oxidesemiconductor as the channel is formed in a simple-structured,low-temperature process similar to a transistor using an amorphoussilicon as a channel. It is known that the transistor using the oxidesemiconductor as the channel has higher mobility than the transistorusing the amorphous silicon as the channel and has a very lowoff-current.

In recent years, due to the advancement in the technology for reducingof the size of a pixel in modern display devices, it has also becomepossible to reduce the width of wiring and the size of transistors.However, there is a limitation to these reductions, and an apertureratio is reduced due to arrangements of a metal layer and asemiconductor layer constituting a pixel circuit. Therefore, thedevelopment for using the oxide semiconductor layer as the channel ofthe transistor in the pixel circuit, which obtains sufficientcharacteristics in spite of its miniaturized size is progressing.

In the transistor using the low-temperature polysilicon as the channel,a silicon layer and a transparent conductive layer (e.g., ITO) used as apixel electrode cannot be directly in contact with each other.Therefore, it is necessary to provide a pedestal of a metal layerbetween the silicon layer and the transparent conductive layer. If sucha pedestal is arranged in a display area of a pixel, there is a problemwhereby an aperture ratio of the pixel is reduced. The technical idearegarding such a contact structure is common to the transistor using theoxide semiconductor as the channel, and the structure forming thetransparent conductive layer on the pedestal of the metal layer iscommonly used.

SUMMARY

A display device according to an embodiment of the present disclosureincludes: a first transistor provided with an oxide semiconductor layer,a first gate electrode facing the oxide semiconductor layer and a firstgate insulating layer between the oxide semiconductor layer and thefirst gate electrode; a first transparent conductive layer overlappingthe first gate electrode and the oxide semiconductor layer in a planview, the first transparent conductive layer being in contact with theoxide semiconductor in a first contact area not overlapping the firstgate electrode; and a second transparent conductive layer overlappingthe first gate electrode, the oxide semiconductor layer and the firsttransparent conductive layer in a plan view, the second transparentconductive layer being connected to the first transparent conductivelayer in a second contact area overlapping the first gate electrode.

A display device according to an embodiment of the present disclosureincludes: a first pixel; and a second pixel to which a pixel signal issupplied from a first wiring. Each of the first pixel and the secondpixel includes: a pixel transistor provided with an oxide semiconductorlayer, a gate electrode facing the oxide semiconductor layer and a gateinsulating layer between the oxide semiconductor layer and the gateelectrode; a first transparent conductive layer overlapping the gateelectrode and the oxide semiconductor layer in a plan view, the firsttransparent conductive layer being in contact with the oxidesemiconductor in a first contact area not overlapping the first gateelectrode; a second transparent conductive layer overlapping the gateelectrode, the oxide semiconductor layer, and the first transparentconductive layer in a plan view, the second transparent conductive layerbeing connected to the first transparent conductive layer in a secondcontact area overlapping the gate electrode. The second transparentconductive layer of the first pixel overlaps the oxide semiconductorlayer of the first pixel and the oxide semiconductor layer of the secondpixel.

A display device according to an embodiment of the present disclosureincludes: a first pixel and a second pixel to which a pixel signal issupplied from a first wiring; and a third pixel and a fourth pixel towhich a pixel signal is supplied from a second wiring adjacent to thefirst pixel. Each of the first pixel and the second pixel includes; afirst transistor provided with an oxide semiconductor layer, a gateelectrode facing the oxide semiconductor layer and a gate insulatinglayer between the oxide semiconductor layer and the gate electrode; afirst transparent conductive layer overlapping the gate electrode andthe oxide semiconductor layer in a plan view, the first transparentconductive layer being in contact with the semiconductor layer in anarea not overlapping the gate electrode; and a second transparentconductive layer overlapping the gate electrode, the oxide semiconductorlayer and the first transparent conductive layer in a plan view, thesecond transparent conductive layer connected to the first transparentconductive layer in a second contact area overlapping the gateelectrode. The first pixel and the third pixel are adjacent to eachother. The second pixel and the fourth pixel are adjacent to each other.The second transparent conductive layer of the first pixel overlaps theoxide semiconductor layer of the first pixel and the oxide semiconductorlayer of the second pixel, and overlaps an oxide semiconductor layer ofthe third pixel.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view showing an outline of a display deviceaccording to an embodiment of the present invention;

FIG. 2 is a plan view showing an outline of a display device accordingto an embodiment of the present invention;

FIG. 3 is a plan view illustrating a layout of each layer in a displaydevice according to an embodiment of the present invention;

FIG. 4 is a plan view illustrating a layout of one or more layers in adisplay device according to an embodiment of the present invention;

FIG. 5 is a plan view illustrating a layout of one or more layers in adisplay device according to an embodiment of the present invention;

FIG. 6 is a plan view illustrating a layout of one or more layers in adisplay device according to an embodiment of the present invention;

FIG. 7 is a plan view illustrating a layout of one or more layers in adisplay device according to an embodiment of the present invention;

FIG. 8 is a plan view illustrating a layout of one or more layers in adisplay device according to an embodiment of the present invention;

FIG. 9 is a plan view illustrating a layout of one or more layers in adisplay device according to an embodiment of the present invention;

FIG. 10 is a plan view illustrating a layout of one or more layers in adisplay device according to an embodiment of the present invention;

FIG. 11 is a plan view illustrating a layout of one or more layers in adisplay device according to an embodiment of the present invention;

FIG. 12 is a plan view illustrating a layout of one or more layers in adisplay device according to an embodiment of the present invention;

FIG. 13 is a plan view illustrating a layout of one or more layers in adisplay device according to an embodiment of the present invention;

FIG. 14 is a cross-sectional view showing an outline of a display deviceaccording to an embodiment of the present invention;

FIG. 15 is a plan view showing an outline of a display device accordingto an embodiment of the present invention;

FIG. 16 is a block diagram showing a circuit configuration of a displaydevice according to an embodiment of the present invention; and

FIG. 17 is a circuit diagram showing a pixel circuit of a display deviceaccording to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below withreference to the drawings. The following disclosure is merely anexample. A configuration that can be easily conceived by a personskilled in the art by appropriately changing the configuration of theembodiment while maintaining the gist of the invention is naturallyincluded in the scope of the present invention. For the sake of clarityof description, the drawings may be schematically represented withrespect to widths, thicknesses, shapes, and the like of the respectiveportions in comparison with actual embodiments. However, the shape shownis merely an example and does not limit the interpretation of thepresent invention. In this specification and each of the drawings, thesame symbols are assigned to the same components as those describedpreviously with reference to the preceding drawings, and a detaileddescription thereof may be omitted as appropriate.

In the embodiments of the present invention, a direction from asubstrate to an oxide semiconductor layer is referred to as upper orabove. On the contrary, a direction from the oxide semiconductor layerto the substrate is referred to as lower or below. As described above,for convenience of explanation, although the phrase “above” or “below”is used for explanation, for example, a vertical relationship betweenthe substrate and the oxide semiconductor layer may be arranged in adifferent direction from that shown in the drawing. In the followingdescription, for example, the expression “the oxide semiconductor layeron the substrate” merely describes the vertical relationship between thesubstrate and the oxide semiconductor layer as described above, andother members may be arranged between the substrate and the oxidesemiconductor layer. Above or below means a stacking order in astructure in which multiple layers are stacked, when it is expressed asa pixel electrode above a transistor, it may be a positionalrelationship where the transistor and the pixel electrode do not overlapeach other in a plan view. On the other hand, when it is expressed as apixel electrode vertically above a transistor, it means a positionalrelationship where the transistor and the pixel electrode overlap eachother in a plan view.

“Display device” refers to a structure configured to display an imageusing electro-optic layers. For example, the term display device mayrefer to a display panel including the electro-optic layer, or it mayrefer to a structure in which other optical members (e.g., polarizingmember, backlight, touch panel, etc.) are attached to a display cell.The “electro-optic layer” can include a liquid crystal layer, anelectroluminescence (EL) layer, an electrochromic (EC) layer, and anelectrophoretic layer, as long as there is no technical contradiction.Therefore, although the embodiments described later will be described byexemplifying the liquid crystal display device including a liquidcrystal layer as the display device, the structure in the presentembodiment can be applied to a display device including the otherelectro-optical layers described above.

The expressions “α includes A, B, or C”, “α includes any of A, B, andC”, and “α includes one selected from a group consisting of A, B, and C”do not exclude the case where α includes multiple combinations of A to Cunless otherwise specified. Furthermore, these expressions do notexclude the case where α includes other elements.

The following embodiments may be combined with each other as long asthere is no technical contradiction.

One of objects of the present embodiment is to realize a brightnessimprovement of a display device.

1. First Embodiment 1-1. Configuration of Display Device 10

A configuration of a display device 10 according to an embodiment of thepresent invention will be described with reference to FIG. 1 to FIG. 13. FIG. 1 is a cross-sectional view showing an outline of a displaydevice according to an embodiment of the present invention. FIG. 2 is aplan view showing an outline of a display device according to anembodiment of the present invention. FIG. 3 to FIG. 13 are plan viewsillustrating layouts of each layer in a display device according to anembodiment of the present invention. The cross-sectional view in FIG. 1is for explaining a layer structure of the display device 10, which maynot exactly match the plan view in FIG. 2 .

As shown in FIG. 1 , the display device 10 includes a substrate SUB. Thedisplay device 10 also includes a transistor Tr1, a transistor Tr2, awiring W, a connecting electrode ZTCO, a pixel electrode PTCO, a commonauxiliary electrode CMTL, and a common electrode CTCO on the substrateSUB. TCO is an abbreviation for Transparent Conductive Oxide. Thetransistor Tr1 is a transistor included in a pixel circuit of thedisplay device 10. The transistor Tr2 is a transistor included in aperipheral circuit. As will be described in detail later, the peripheralcircuit is a circuit configured to drive the pixel circuit.

1-2. Configuration of Transistor Tr1

The transistor Tr1 includes an oxide semiconductor layer OS, a gateinsulating layer GI1, and a gate electrode GL1. The gate electrode GL1faces the oxide semiconductor layer OS. The gate insulating layer GI1 isprovided between the oxide semiconductor layer OS and the gate electrodeGL1. In the present embodiment, although a top gate type transistor inwhich the oxide semiconductor layer OS is provided closer to thesubstrate SUB than the gate electrode GL1 is exemplified, a bottom gatetype transistor in which a positional relationship between the gateelectrode GL1 and the oxide semiconductor layer OS is reversed may beapplied.

The oxide semiconductor layer OS includes oxide semiconductor layersOS1, OS2. The oxide semiconductor layer OS1 is an oxide semiconductorlayer in an area overlapping the gate electrode GL1 in a plan view. Theoxide semiconductor layer OS1 functions as a semiconductor layer and isswitched between a conductive state and a non-conductive state accordingto a voltage supplied to the gate electrode GL1. That is, the oxidesemiconductor layer OS1 functions as a channel for the transistor Tr1.The oxide semiconductor layer OS2 functions as a conductive layer. Theoxide semiconductor layers OS1, OS2 are layers formed from the sameoxide semiconductor layer. For example, the oxide semiconductor layerOS2 is a low resistance oxide semiconductor layer formed by dopingimpurities into a layer which has the same physical properties as theoxide semiconductor layer OS1.

An insulating layer IL2 is provided above the gate electrode GL1. Awiring W1 is provided above the insulating layer IL2. The wiring W1 isconnected to the oxide semiconductor layer OS2 via an opening WCONprovided in the insulating layer IL2 and the gate insulating layer GI1.A data signal related to pixel gradation is transmitted to the wiringW1. An insulating layer IL3 is provided above the insulating layer IL2and the wiring W1. The connecting electrode ZTCO is provided above theinsulating layer IL3. The connecting electrode ZTCO is connected to theoxide semiconductor layered OS2 via an opening ZCON provided in theinsulating layers IL3, IL2, and the gate insulating layer GI1. Theconnecting electrode ZTCO is in contact with the oxide semiconductorlayer OS2 at the bottom of the opening ZCON. The connecting electrodeZTCO is a transparent conductive layer.

An area where the connecting electrode ZTCO and the oxide semiconductorlayers OS2 are in contact with each other is referred to as a firstcontact area CON1. The connecting electrode ZTCO may be referred to as a“first transparent conductive layer”. As will be described in detaillater, the first transparent conductive layer is in contact with theoxide semiconductor layer OS2 in the first contact area CON1 notoverlapping the gate electrode GL1 and the wiring W1 in a plan view. Thefirst contact area CON1 is included in the display area of a pixel in aplan view.

For example, when a transparent conductive layer such as an ITO layer isformed in contact with a semiconductor layer such as a silicon layer, asurface of the semiconductor layer is oxidized by a process gas oroxygen ions at the time of a deposition of an ITO film. Since an oxidelayer formed on the surface of the semiconductor layer is highresistance, a contact resistance between the semiconductor layer and thetransparent conductive layer is increased. As a result, there is adefect in an electrical contact between the semiconductor layer and thetransparent conductive layer. On the other hand, even if the abovetransparent conductive layer is formed so as to be in contact with theoxide semiconductor layer, a high resistance oxide layer as describedabove is not formed on a surface of the oxide semiconductor layer.Therefore, there is no defect in the electrical contact between theoxide semiconductor layer and the transparent conductive layer.

An insulating layer IL4 is provided above the connecting electrode ZTCO.The insulating layer IL4 eases (flattens) a step formed from a structureprovided below the insulating layer IL4. The insulating layer IL4 may bereferred to as a planarization film. The pixel electrode PTCO isprovided above the insulating layer IL4. The pixel electrode PTCO isconnected to the connecting electrode ZTCO via an opening PCON providedin the insulating layer IL4. An area where the connecting electrode ZTCOand the pixel electrode PTCO are in contact with each other is referredto as a second contact area CON2. The second contact area CON2 overlapsthe gate electrode GL1 in a plan view. The pixel electrode PTCO is atransparent conductive layer.

An insulating layer IL5 is provided above the pixel electrode PTCO. Thecommon auxiliary electrode CMTL and the common electrode CTCO areprovided above the insulating layer IL5. That is, the pixel electrodePTCO faces the common electrode CTCO via the insulating layer IL5. Thecommon electrode CTCO is connected to the common auxiliary electrodeCMTL at the opening PCON (in the second contact area CON2). As will bedescribed in detail later, the common auxiliary electrode CMTL and thecommon electrode CTCO have different patterns respectively when seen aplan view. The common auxiliary electrode CMTL is a metal layer. Thecommon electrode CTCO is a transparent conductive layer. The electricresistance of the common auxiliary electrode CMTL is lower than theelectric resistance of the common electrode CTCO. The common auxiliaryelectrode CMTL also functions as a light-shielding layer. For example,the common auxiliary electrode CMTL shields light from adjacent pixelsto suppress an occurrence of color mixing. A spacer SP is provided abovethe common electrode CTCO.

The spacer SP is provided for a part of the pixels. For example, thespacer SP may be provided for any one of a blue pixel, a red pixel and agreen pixel. However, the spacer SP may be provided for all the pixels.A height of the spacer SP is half the height of a cell gap. A spacer isalso provided on a counter substrate, and the spacer on the countersubstrate and the above spacer SP overlap in a plan view.

A light-shielding layer LS is provided between the transistor Tr1 andthe substrate SUB. In the present embodiment, light-shielding layersLS1, LS2 are provided as the light-shielding layer LS. However, thelight-shielding layer LS may be formed of only the light-shielding layerLS1 or LS2. In a plan view, the light-shielding layer LS is provided inan area where the gate electrode GL1 and the oxide semiconductor layerOS overlap. That is, in a plan view, the light-shielding layer LS isprovided in an area overlapping the oxide semiconductor layer OS1. Thelight-shielding layer LS suppresses the light incident from thesubstrate SUB side from reaching the oxide semiconductor layer OS1. Inthe case where a conductive layer is used as the light-shielding layerLS, a voltage may be applied to the light-shielding layer LS to controlthe oxide semiconductor layer OS1. In the case where a voltage isapplied to the light-shielding layer LS, the light-shielding layer LSand the gate electrode GL1 may be connected by a peripheral area of thepixel circuit. In a plan view, the above first contact area CON1 isprovided in an area not overlapping the light-shielding layer LS.

1-3. Configuration of Transistor Tr2

The transistor Tr2 has a p-type transistor Tr2-1 and an n-typetransistor Tr2-2. The transistor Tr2 may be referred to as a “secondtransistor.”

The p-type transistor Tr2-1 and the n-type transistor Tr2-2 both includea gate electrode GL2, a gate insulating layer GI2, and a semiconductorlayer S (S1 and S2, or S1, S2 and S3). The gate electrode GL2 faces thesemiconductor layer S. The gate insulating layer GI2 is provided betweenthe semiconductor layer S and the gate electrode GL2. In the presentembodiment, although a bottom gate type transistor in which the gateelectrode GL2 is provided closer to the substrate SUB than thesemiconductor layer S is exemplified, a top gate type transistor inwhich a positional relationship between the semiconductor layer S andthe gate electrode GL2 is reversed may be used as the display device.The gate electrode GL2 may be referred to as a “second gate electrode”.The gate insulating layer GI2 may be referred to as a “second gateinsulating layer”.

The semiconductor layer S of the p-type transistor Tr2-1 includessemiconductor layers S1 and S2. The semiconductor layer S of the n-typetransistor Tr2-2 includes the semiconductor layers S1, S2 and S3. Thesemiconductor layer S1 is a semiconductor layer overlapping the gateelectrode GL2 in a plan view. The semiconductor layer S1 functions as achannel for the transistors Tr2-1 and Tr2-2. The semiconductor layer S2functions as a conductive layer. The semiconductor layer S3 functions asa conductive layer with a higher resistance than the semiconductor layerS2. The semiconductor layer S3 suppresses hot carrier degradation byattenuating hot carriers intruding toward the semiconductor layer S1.

An insulating layer IL1 and the gate insulating layer GI1 are providedon the semiconductor layer S. In the transistor Tr2, the gate insulatinglayer GI1 simply functions as an interlayer film. A wiring W2 isprovided above these insulating layers. The wiring W2 is connected tothe semiconductor layer S via an opening provided in the insulatinglayer IL1 and the gate insulating layer GI1. The insulating layer IL2 isprovided on the wiring W2. The wiring W1 is provided on the insulatinglayer IL2. The wiring W1 is connected to the wiring W2 via an openingprovided in the insulating layer IL2.

The gate electrode GL2 and the light-shielding layer LS2 are the samelayer. The wiring W2 and the gate electrode GL1 are the same layer. Thesame layer means that multiple members are formed from one patternedlayer.

1-4. Plane Layout of Display Device 10

A plane layout of a pixel of the display device 10 will be describedwith reference to FIG. 2 to FIG. 13 . In FIG. 2 , the pixel electrodePTCO, the common auxiliary electrode CMTL, the common electrode CTCO,and the spacer SP are omitted. The plane layout of the pixel electrodePTCO, the common auxiliary electrode CMTL, and the common electrode CTCOare shown in FIG. 11 to FIG. 13 , respectively.

As shown in FIG. 2 and FIG. 3 , the light-shielding layer LS extends ina direction D1. A shape of the light-shielding layer LS may be differentdepending on the pixel. In the present embodiment, a protruding part PJTprotruding in a direction D2 is provided from a part of thelight-shielding layer LS extending in the direction D1. As shown in FIG.5 , the light-shielding layer LS is provided in an area including thearea where the gate electrode GL1 and the oxide semiconductor layer OSoverlap in a plan view. The gate electrode GL1 can also be referred toas a “gate line.”

As shown in FIG. 2 , FIG. 4 , and FIG. 5 , the oxide semiconductor layerOS extends in the direction D2. The gate electrode GL1 extends in thedirection D1 so as to intersect the oxide semiconductor layer OS. Apattern of the gate electrode GL1 is provided inside a pattern of thelight-shielding layer LS. In other words, the oxide semiconductor layersOS is formed in a long shape intersecting the gate electrode GL1.

As shown in FIG. 2 , FIG. 6 , and FIG. 7 , the opening WCON is providedin an area overlapping the wiring W1 near an upper end of the pattern ofthe oxide semiconductor layer OS. A main part of the pattern of theoxide semiconductor layer OS extends in the direction D2 between a pairof the adjacent wirings W1. The remaining part of the pattern of theoxide semiconductor layer OS extends obliquely in the direction D1 andthe direction D2 from the main part and overlaps the opening WCON.

As shown in FIG. 2 and FIG. 7 , multiple wirings W1 extend in thedirection D2. In the case where the adjacent wirings W1 need to bedescribed separately, the adjacent wiring W1 is referred to as a wiringW1-1 (first wiring) and a wiring W1-2 (second wiring). In this case, itcan be said that the main part of the oxide semiconductor layer OSextends in the direction D2 between the first wiring W1-1 and the secondwiring W1-2, and intersects the gate electrode GL1. In other words, theoxide semiconductor layer OS is provided in a long shape in thedirection D2 (shape having a longitudinal) and connected to the wiringW1-1 (the first wiring) at one end in a longitudinal direction of theoxide semiconductor layer OS.

As shown in FIG. 2 , FIG. 8 , and FIG. 9 , the opening ZCON is providednear a lower end of the pattern of the oxide semiconductor layer OS. Theopening ZCON is provided in an area overlapping the pattern of the oxidesemiconductor layer OS and not overlapping the gate electrode GL1. Theopening ZCON is provided in an area overlapping the connecting electrodeZTCO. The connecting electrode ZTCO overlaps the gate electrode GL1 andthe oxide semiconductor layer OS between the wiring W1-1 and the wiringW1-2. Therefore, the connecting electrode ZTCO is in contact with theoxide semiconductor layer OS in the opening ZCON (the first contact areaCON1) not overlapping the gate electrode GL1.

In other words, the oxide semiconductor layer OS is connected to theconnecting electrode ZTCO (the first transparent conductive layer) atthe other end in the longitudinal direction of the oxide semiconductorlayer OS. The connecting electrode ZTCO is formed in a long shapeextending in the direction D2 similar to the oxide semiconductor layerOS. In the direction D1, a width of the connecting electrode ZTCO issmaller than a width of the oxide semiconductor layer OS.

As shown in FIG. 2 , FIG. 7 , and FIG. 8 , the oxide semiconductor layerOS is in contact with the wiring W1 at the opposite side of the openingZCON with respect to the gate electrode GL1. The opening ZCON does notoverlap with the light-shielding layer LS.

As shown in FIG. 2 , FIG. 10 , and FIG. 11 , the opening PCON isprovided near an upper end of a pattern of the connecting electrodeZTCO. The opening PCON is provided in an area overlapping the pattern ofthe gate electrode GL1 and the pattern of the connecting electrode ZTCO.The opening PCON is provided in an area overlapping the pixel electrodePTCO. The pixel electrode PTCO overlaps the gate electrode GL1, theoxide semiconductor layer OS, and the connecting electrode ZTCO betweenthe wiring W1-1 and the wiring W1-2. Therefore, the pixel electrode PTCOis in contact with the connecting electrode ZTCO in the opening PCON(the second contact area CON2) overlapping the gate electrode GL1.

The pixel electrode PTCO extends in a translucent area as describedbelow. The pixel electrode PTCO may be referred to as a “secondtransparent conductive layer”. In other words, the pixel electrode PTCOis formed in a long shape extending in the direction D2 similar to theoxide semiconductor layer OS and the wiring W1-1 (the first wiring). Inthe direction D1, a width of the pixel electrode PTCO is larger than thewidth of the oxide semiconductor layer OS at a part where the openingPCON is provided.

As shown in FIG. 11 , the connecting electrode ZTCO is formed in a longshape extending along the wiring W1-1. In the direction D1, a width ofthe opening PCON constituting the second contact area CON2 is largerthan the width of the connecting electrode ZTCO. The connectingelectrode ZTCO entirely overlaps the pixel electrode PTCO in a planview.

As shown in FIG. 11 , the pixel electrodes PTCO are aligned in thedirection D2. Of the pixels adjacent to the direction D2, one pixel maybe referred to as a “first pixel”, and the other pixel may be referredto as a “second pixel”. For example, the first pixel is a pixelcorresponding to the upper pixel electrode PTCO among the pixelelectrodes PTCO aligned in the direction D2 in FIG. 11 , and the secondpixel is a pixel corresponding to the lower pixel electrode PTCO amongthe pixel electrodes PTCO aligned in the direction D2 in FIG. 11 . Inthis case, the first pixel and the second pixel are supplied with apixel signal from the wiring W1-1.

The pixel electrodes PTCO are aligned in the direction D1. A pixeladjacent in the direction D1 with respect to the above first pixel isreferred to as a “third pixel”, and a pixel adjacent in the direction D1with respect to the second pixel is referred to as a “fourth pixel”. Thethird pixel and the fourth pixel are adjacent to each other in thedirection D2. The third pixel and the fourth pixel are supplied with thepixel signal from the wiring W1-2 (the second wiring) adjacent to thewiring W1-1.

As described above, each of the first pixel, the second pixel, the thirdpixel, and the fourth pixel includes the transistor Tr1 (pixeltransistor), the connecting electrode ZTCO, and the pixel electrodePTCO.

The transistor Tr1 includes the oxide semiconductor layer OS, the gateelectrode GL1 facing the oxide semiconductor layer OS, and the gateinsulating layer GI1 between the oxide semiconductor layer OS and thegate electrode GL1. The connecting electrode ZTCO overlaps the gateelectrode GL1 and the oxide semiconductor layer OS and contacts theoxide semiconductor layer OS in the opening ZCON (the first contact areaCON1) not overlapped with the gate electrode GL1 in a plan view. Thepixel electrode PTCO overlaps the gate electrode GL1, the oxidesemiconductor layer OS, and the connecting electrode ZTCO and isconnected to the connecting electrode ZTCO in the opening PCONoverlapping the gate electrode GL1 (the second contact area CON2) in aplan view.

The pixel electrode PTCO of the first pixel provided on the upper sidein FIG. 11 overlaps the oxide semiconductor layer OS of the first pixeland the oxide semiconductor layer OS of the second pixel provided on thelower side of the first pixel in a plan view. The pixel electrode PTCOof the first pixel also overlaps a part of the oxide semiconductor layerOS of the fourth pixel in a plan view.

As shown in FIG. 12 , the common auxiliary electrode CMTL is provided ina grid shape so as to surround the periphery of a pixel area. That is,the common auxiliary electrode CMTL is provided commonly for multiplepixels. In other words, the common auxiliary electrode CMTL has anopening OP. The opening OP is provided to expose the pixel electrodePTCO. A pattern of the opening OP is provided inside the pattern of thepixel electrode PTCO. An area provided with the opening OP correspondsto a display area. That is, the opening ZCON is included in the displayarea. The display area means an area in which a user can see light froma pixel. For example, a frame area that is shielded by a metal layer andunperceivable to the user is not included in the display area. That is,the above display area may be referred to as a “translucent area (oropening area)”.

As shown in FIG. 13 , the common electrode CTCO is provided commonly formultiple pixels. A slit SL is provided in an area corresponding to theabove opening OP. The slit SL has a curved shape (longitudinally longS-shape). A tip of the slit SL has a shape in which a width orthogonalto an extending direction of the tip is reduced. Referring to FIG. 1 andFIG. 13 , the common electrode CTCO has the slit SL at a position facingthe pixel electrode PTCO.

1-5. Materials of Each Member of Display Device 10

A rigid substrate having light transmittance and no flexibility, such asa glass substrate, a silica substrate, and a sapphire substrate can beused as the substrate SUB. On the other hand, in the case where thesubstrate SUB needs to have a flexibility, a flexible substratecontaining a resin and having flexibility, such as a polyimidesubstrate, an acrylic substrate, a siloxane substrate, or a fluororesinsubstrate can be used as the substrate SUB. In order to improve the heatresistance of the substrate SUB, impurities may be introduced into theabove resin.

General metal materials can be used as the gate electrodes GL1, GL2, thewirings W1, W2, the light-shielding layer LS, and the common auxiliaryelectrode CMTL. For example, aluminum (Al), titanium (Ti), chromium(Cr), cobalt (Co), nickel (Ni), molybdenum (Mo), hafnium (Hf), tantalum(Ta), tungsten (W), bismuth (Bi), and silver (Ag), or alloys orcompounds thereof are used as members of these electrodes and the like.The above materials may be used in a single layer or a stacked layer asthe members of the above electrodes and the like.

For example, a stacked structure of Ti/Al/Ti is used as the gateelectrode GL1. In the present embodiment, the cross-sectional shape of apattern end of the gate electrode GL1 having the above stacked structureis a forward taper shape.

General insulating materials can be used as the gate insulating layersGI1, GI2, and the insulating layers IL1 to IL5. For example, inorganicinsulating layers such as silicon oxide (SiO_(x)), silicon oxynitride(SiO_(x)N_(y)), silicon nitride (SiN_(x)), silicon nitride oxide(SiN_(x)O_(y)), aluminum oxide (AlO_(x)), aluminum oxynitride(AlO_(x)N_(y)), aluminum nitride oxide (AlN_(x)O_(y)), aluminum nitride(AlN_(x)), and the like can be used as the insulating layers IL1 to IL3,and IL5. Low-defect insulating layers can be used as these insulatinglayers. Organic insulating materials such as a polyimide resin, anacrylic resin, an epoxy resin, a silicone resin, a fluororesin, or asiloxane resin can be used as the insulating layer IL4. The aboveorganic insulating materials may be used as the gate insulating layersGI1, GI2, and the insulating layers IL1 to IL3, IL5. The above materialsmay be used in a single layer or a stacked layer as a member of theinsulating layer and the like.

SiO_(x) with a thickness of 100 nm is used as the gate insulating layerGI1 as an example of the above insulating layer. SiO_(x)/SiN_(x)/SiO_(x)with a total thickness of 600 nm to 700 nm is used as the insulatinglayer IL1. SiO_(x)/SiN_(x) with a total thickness of 60 nm to 100 nm isused as the gate insulating layer GI2. SiO_(x)/SiN_(x)/SiO_(x) with atotal thickness of 300 nm to 500 nm is used as the insulating layer IL2.SiO_(x) with a total thickness of 200 nm to 500 nm (single layer),SiN_(x) (single layer), or a stacked layer thereof is used as theinsulating layer IL3. The organic layer with a thickness of 2 μm to 4 μmis used as the insulating layer IL4. SiN_(x) (single layer) with athickness of 50 nm to 150 nm is used as the insulating layer IL5.

The above SiO_(x)N_(y) and AlO_(x)N_(y) are silicone compounds andaluminum compounds containing nitrogen (N) in a smaller ratio (x>y) thanoxygen (O). The above SiN_(x)O_(y) and AlN_(x)O_(y) are siliconcompounds and aluminum compounds containing oxygen in a smaller ratio(x>y) than nitrogen.

A metal oxide having semiconductor characteristics can be used as theoxide semiconductor layer OS. The oxide semiconductor layer OS has lighttransmittance. For example, an oxide semiconductor containing indium(In), gallium (Ga), zinc (Zn), and oxygen (O) can be used as the oxidesemiconductor layer OS. In particular, an oxide semiconductor having acomposition ratio of In:Ga:Zn:O=1:1:1:4 can be used. However, the oxidesemiconductor containing In, Ga, Zn, and O used in the presentembodiment is not limited to the above composition, and an oxidesemiconductor having a composition different from that described abovecan also be used. For example, the ratio of In may be larger than thatdescribed above to improve mobility. The ratio of Ga may be larger toincrease the band gap and reduce the influence of light irradiation.

Other elements may be added to the oxide semiconductor containing In,Ga, Zn, and O. For example, a metal element such as Al or Sn may beadded to the oxide semiconductor. In addition to the oxide semiconductordescribed above, an oxide semiconductor containing In and Ga (IGO), anoxide semiconductor containing In and Zn (IZO), an oxide semiconductorcontaining In, Sn, and Zn (ITZO), and an oxide semiconductor containingIn and W may be used as the oxide semiconductor layer OS. The oxidesemiconductor layer OS may be amorphous or crystalline. The oxidesemiconductor layer OS may be a mixed phase of amorphous andcrystalline.

A transparent conductive layer is used as the connecting electrode ZTCO,the pixel electrode PTCO, and the common electrode CTCO. A mixture ofindium oxide and tin oxide (ITO) and a mixture of indium oxide and zincoxide (IZO) can be used as the transparent conductive layer. Materialsother than the above may be used as the transparent conductive layer.

As described above, according to the display device 10 according to thepresent embodiment, conduction between the oxide semiconductor layer OSand the connecting electrode ZTCO can be ensured by directly contactingthe oxide semiconductor layer OS and the connecting electrode ZTCO inthe transistor Tr1. Therefore, there is no need to provide a metal layerbetween the oxide semiconductor layer OS and the connecting electrodeZTCO. With this configuration, since light is not blocked in the openingZCON (the first contact area CON1), it is possible to suppress adecrease in the opening ratio. The oxide semiconductor layer has lighttransmittance. Therefore, in the present embodiment, although the oxidesemiconductor layer is provided in an opening area of the pixel area,light from the backlight passes through the oxide semiconductor layer.Therefore, the reduction in the light transmittance in the opening areadue to the oxide semiconductor layer provided in the opening area isreduced as much as possible. Since the oxide semiconductor layer OS haslight transmittance, it is less likely to cause unevenness intransmitted light, unlike the silicon layer. Since the oxidesemiconductor layer OS is provided in the display area, it is possibleto suppress the occurrence of display unevenness.

2. Second Embodiment

A configuration of a display device 10A according to an embodiment ofthe present invention will be described with reference to FIG. 14 . FIG.14 is a cross-sectional view showing an outline of a display deviceaccording to an embodiment of the present invention. Although thedisplay device 10A shown in FIG. 14 is similar to the display device 10shown in FIG. 1 , the positional relationship between the pixelelectrode PTCO and the common electrode CTCO is different.

As shown in FIG. 14 , the common auxiliary electrode CMTL and the commonelectrode CTCO are provided above the insulating layer IL4. Theinsulating layer IL5 is provided above the common auxiliary electrodeCMTL and the common electrode CTCO. The pixel electrode PTCO is providedabove the insulating layer IL5. The pixel electrode PTCO is connected tothe connecting electrode ZTCO via the opening PCON provided in theinsulating layers IL4 and IL5. As described above, the pixel electrodePTCO may be provided above the common electrode CTCO.

According to the display device 10A of the present embodiment, the sameeffects as those of the display device 10 of the first embodiment can beobtained.

Third Embodiment

An entire configuration of the display device described in the firstembodiment and the second embodiment will be described with reference toFIG. 15 to FIG. 17 .

Outline of Display Device 20B

FIG. 15 is a plan view showing an outline of a display device accordingto an embodiment of the present invention. As shown in FIG. 15 , adisplay device 20B includes an array substrate 300B, a seal part 400B, acounter substrate 500B, a flexible printed circuit board 600B (FPC600B), and an IC chip 700B. The array substrate 300B and the countersubstrate 500B are bonded by the seal part 400B. Multiple pixel circuits310B are arranged in a matrix in a liquid crystal area 22B surrounded bythe seal part 400B. The liquid crystal area 22B is an area overlapping aliquid crystal element 410B described later in a plan view. The liquidcrystal area 22B is an area configured to contribute to display. Theliquid crystal area 22B may be referred to as a “display area”. Thetransistor Tr1 (first transistor) is provided in the liquid crystal area22B (display area).

A seal area 24B provided with the seal part 400B is an area around theliquid crystal area 22B. The FPC 600B is provided in a terminal area26B. The terminal area 26B is an area where the array substrate 300B isexposed from the counter substrate 500B and provided outside the sealarea 24B. The exterior side of the seal area means outside the areaprovided with the seal part 400B and outside the area surrounded by theseal part 400B. The IC chip 700B is provided on the FPC 600B. The ICchip 700B supplies a signal for driving each pixel circuit 310B. Theseal area 24B or an area combined with the seal area 24B and theterminal area 26B is an area that surrounds the liquid crystal area 22B(display area). These areas may be referred to as a “frame area”. Thetransistor Tr2 (the second transistor) is provided in the frame area.

Circuit Configuration of Display Device 20B

FIG. 16 is a block diagram showing a circuit configuration of a displaydevice according to an embodiment of the present invention. As shown inFIG. 16 , a source driver circuit 320B and the liquid crystal area 22Bwhere the pixel circuit 310B is arranged are adjacent in the directionD1 (column direction), and the gate driver circuit 330B and the liquidcrystal area 22B are adjacent in the direction D2 (row direction). Thesource driver circuit 320B and the gate driver circuit 330B are providedin the seal area 24B described above. However, the area where the sourcedriver circuit 320B and the gate driver circuit 330B are provided is notlimited to the seal area 24B, and it may be any area as long as it isthe outside the area provided with the pixel circuit 310B.

A source wiring 321B extends in the direction D1 from the source drivercircuit 320B and is connected to the multiple pixel circuits 310Barranged in the direction D1. A gate wiring 331B extends in thedirection D2 from the gate driver circuit 330B and is connected to themultiple pixel circuits 310B arranged in the direction D2.

The terminal area 26B is provided with a terminal part 333B. Theterminal part 333B and the source driver circuit 320B are connected by aconnecting wiring 341B. Similarly, the terminal part 333B and the gatedriver circuit 330B are connected by the connecting wiring 341B. Whenthe FPC 600B is connected to the terminal part 333B, an external deviceto which the FPC 600B is connected and the display device 20B areconnected, and each pixel circuit 310B provided in the display device20B is driven by a signal from the external device.

The transistor Tr1 shown in the first embodiment and the secondembodiment is used for the pixel circuit 310B. The transistor Tr2 shownin the first embodiment and the second embodiment is applied to thetransistor included in the source driver circuit 320B and the gatedriver circuit 330B.

Pixel Circuit 310B of Display Device 20B

FIG. 17 is a circuit diagram showing a pixel circuit of a display deviceaccording to an embodiment of the present invention. As shown in FIG. 17, the pixel circuit 310B includes elements such as a transistor 800B, astorage capacitor 890B, and the liquid crystal element 410B. Oneelectrode of the storage capacitor 890B is the pixel electrode PTCO andthe other electrode is the common electrode CTCO. Similarly, oneelectrode of the liquid crystal element 410B is the pixel electrode PTCOand the other electrode is the common electrode CTCO. The transistor800B includes a first gate electrode 810B, a first source electrode830B, and a first drain electrode 840B. The first gate electrode 810B isconnected to the gate wiring 331B. The first source electrode 830B isconnected to the source wiring 321B. The first drain electrode 840B isconnected to the storage capacitor 890B and the liquid crystal element410B. The transistor Tr1 shown in the first embodiment and the secondembodiment is applied to the transistor 800B shown in FIG. 17 . In thepresent embodiment, for convenience of explanation, although 830B isreferred to as a source electrode and 840B is referred to as a drainelectrode, the function of each electrode as a source and a drain may bereplaced.

Each of the embodiments described above as an embodiment of the presentinvention can be appropriately combined and implemented as long as theydo not contradict each other. Further, the addition, deletion, or designchange of components as appropriate by those skilled in the art based oneach embodiment are also included in the scope of the present inventionas long as they are provided with the gist of the present invention.

It is understood that, even if the effect is different from thoseprovided by each of the above-described embodiments, the effect obviousfrom the description in the specification or easily predicted by personsordinarily skilled in the art is apparently derived from the presentinvention.

What is claimed is:
 1. A display device comprising: a first transistorprovided with an oxide semiconductor layer, a first gate electrodefacing the oxide semiconductor layer and a first gate insulating layerbetween the oxide semiconductor layer and the first gate electrode; afirst transparent conductive layer overlapping the first gate electrodeand the oxide semiconductor layer in a plan view, the first transparentconductive layer being in contact with the oxide semiconductor in afirst contact area not overlapping the first gate electrode; and asecond transparent conductive layer overlapping the first gateelectrode, the oxide semiconductor layer and the first transparentconductive layer in a plan view, the second transparent conductive layerbeing connected to the first transparent conductive layer in a secondcontact area overlapping the first gate electrode, wherein the secondtransparent conductive layer extends to a translucent area of a pixel,and the first contact area is included in the translucent area in a planview.
 2. The display device according to claim 1, further comprising afirst wiring to which a signal related to pixel gradation istransmitted, wherein the first contact area is provided in an area notoverlapping the first gate electrode and the first wiring.
 3. A displaydevice comprising: a first transistor provided with an oxidesemiconductor layer, a first gate electrode facing the oxidesemiconductor layer and a first gate insulating layer between the oxidesemiconductor layer and the first gate electrode; a first transparentconductive layer overlapping the first gate electrode and the oxidesemiconductor layer in a plan view, the first transparent conductivelayer being in contact with the oxide semiconductor in a first contactarea not overlapping the first gate electrode; a second transparentconductive layer overlapping the first gate electrode, the oxidesemiconductor layer and the first transparent conductive layer in a planview, the second transparent conductive layer being connected to thefirst transparent conductive layer in a second contact area overlappingthe first gate electrode; and a light-shielding layer provided in anarea where at least the first gate electrode and the oxide semiconductorlayer overlap in a plan view, wherein the first contact area is providedin an area not overlapping the light-shielding layer.
 4. The displaydevice according to claim 3, further comprising a second transistorprovided with a semiconductor layer, a second gate electrode facing thesemiconductor layer and a second gate insulating layer between thesemiconductor layer and the second gate electrode, wherein the secondgate electrode and the light-shielding layer are provided in the samelayer.
 5. The display device according to claim 4, further comprising awiring connected to the semiconductor layer, wherein the first gateelectrode and the wiring are provided in the same layer.
 6. The displaydevice according to claim 4, further comprising: a display areaconfigured to contribute to display; and a frame area surrounding thedisplay area, wherein the first transistor is provided in the displayarea, and the second transistor is provided in the frame area.
 7. Thedisplay device according to claim 2, wherein the oxide semiconductorlayer is formed in a long shape intersecting the gate electrode,connected to the first wiring at a first end of the oxide semiconductorlayer in a longitudinal direction of the oxide semiconductor layer, andconnected to the first transparent conductive layer at a second end ofthe oxide semiconductor, and the second end is opposite to the first endwith respect to the oxide semiconductor layer in the longitudinaldirection.
 8. The display device according to claim 7, wherein the firsttransparent conductive layer is formed in a long shape extending in thesame direction as the oxide semiconductor layer, and a width of thefirst transparent conductive layer is smaller than a width of the oxidesemiconductor layer in a direction orthogonal to the longitudinaldirection.
 9. The display device according to claim 8, wherein thesecond transparent conductive layer is formed in a long shape extendingin the same direction as the oxide semiconductor layer, and a width ofthe second transparent conductive layer is larger than the width of theoxide semiconductor layer in a direction orthogonal to the longitudinaldirection.
 10. The display device according to claim 7, wherein thesecond transparent conductive layer is formed in a long shape extendingin the same direction as the oxide semiconductor layer, and a width ofthe second transparent conductive layer is larger than a width of theoxide semiconductor layer in a direction orthogonal to the longitudinaldirection.
 11. The display device according to claim 2, wherein thefirst transparent conductive layer is formed in a long shape extendingalong the first wiring, and a width of an opening constituting thesecond contact area is larger than a width of the first transparentconductive layer in a direction orthogonal to the longitudinal directionof the first transparent conductive layer.
 12. The display deviceaccording to claim 4, further comprising a display area configured tocontribute to display and a frame area surrounding the display area,wherein the first transistor is provided in the display area, and thesecond transistor is provided in the frame area.
 13. The display deviceaccording to claim 2, wherein the oxide semiconductor layer is formed ina long shape intersecting the first gate electrode, connected to thefirst wiring at one end of the oxide semiconductor layer in alongitudinal direction of the oxide semiconductor layer, and connectedto the first transparent conductive layer at the other end of the oxidesemiconductor layer in the longitudinal direction of the oxidesemiconductor layer.
 14. The display device according to claim 13,wherein the first transparent conductive layer is formed in a long shapeextending in the same direction as the oxide semiconductor layer, and awidth of the first transparent conductive layer is smaller than a widthof the oxide semiconductor layer in a direction orthogonal to thelongitudinal direction.
 15. The display device according to claim 14,wherein the second transparent conductive layer is formed in a longshape extending in the same direction as the oxide semiconductor layer,and a width of the second transparent conductive layer is larger than awidth of the oxide semiconductor layer in a direction orthogonal to thelongitudinal direction.
 16. A display device comprising: a first pixeland a second pixel to both of which pixel signals are supplied from afirst wiring, wherein each of the first pixel and the second pixelincludes: a pixel transistor provided with an oxide semiconductor layer,a gate electrode facing the oxide semiconductor layer and a gateinsulating layer between the oxide semiconductor layer and the gateelectrode; a first transparent conductive layer overlapping the gateelectrode and the oxide semiconductor layer in a plan view, the firsttransparent conductive layer being in contact with the oxidesemiconductor in a first contact area not overlapping the first gateelectrode; and a second transparent conductive layer overlapping thegate electrode, the oxide semiconductor layer, and the first transparentconductive layer in a plan view, the second transparent conductive layerbeing connected to the first transparent conductive layer in a secondcontact area overlapping the gate electrode; and the second transparentconductive layer of the first pixel overlaps the oxide semiconductorlayer of the first pixel and the oxide semiconductor layer of the secondpixel.
 17. The display device according to claim 16, wherein the secondtransparent conductive layer of the first pixel and the secondtransparent conductive layer of the second pixel face a common electrodevia an insulating film.
 18. The display device according to claim 17,wherein the common electrode has a slit at a position facing the secondtransparent conductive layer of the first pixel and the secondtransparent conductive layer of the second pixel.
 19. A display devicecomprising: a first pixel and a second pixel to both of which pixelsignals are supplied from a first wiring; and a third pixel and a fourthpixel to both of which pixel signals are supplied from a second wiringadjacent to the first and the second pixel, wherein each of the firstpixel, second pixel, third pixel and the fourth pixel includes; a firsttransistor provided with an oxide semiconductor layer, a gate electrodefacing the oxide semiconductor layer and a gate insulating layer betweenthe oxide semiconductor layer and the gate electrode; a firsttransparent conductive layer overlapping the gate electrode and theoxide semiconductor layer in a plan view, the first transparentconductive layer being in contact with the semiconductor layer in anarea not overlapping the gate electrode; and a second transparentconductive layer overlapping the gate electrode, the oxide semiconductorlayer and the first transparent conductive layer in a plan view, thesecond transparent conductive layer connected to the first transparentconductive layer in a second contact area overlapping the gateelectrode, the first pixel and the third pixel are adjacent to eachother, the second pixel and the fourth pixel are adjacent to each other,and the second transparent conductive layer of the first pixel overlapsthe oxide semiconductor layer of the first pixel and the oxidesemiconductor layer of the second pixel, and overlaps an oxidesemiconductor layer of the fourth pixel.